What is Nackgammon?

Nackgammon (Nack for short) is played with exactly the same rules as
normal backgammon, except for the starting position. Each player removes
a checker from their mid point and six point, and places those 2 checkers
on their 23 point instead. This variant tends to lead to games which
place more emphasis on priming and back games, with less emphasis on
attacking and blitzing.